1. Field of the Invention
The present invention relates to an axial fan unit in which two or more axial fans are coaxially arranged with and connected to each other, and an axial fan for use in the axial fan unit.
2. Description of the Related Art
Axial fans have been used for cooling electronic components in electronic devices such as personal computers and servers. Each axial fan is usually connected to an external power supply via wires which are connected to a motor in a housing of the axial fan and pulled out to the outside of the housing.
Two or more axial fans coaxially arranged with and connected to each other form an axial fan unit. A wire for current from the power supply and a wire connected to the ground are connected to the motor of each axial fan. In addition, a wire for a control signal used in, for example, PWM (pulse width modulation) control and a wire for a sensor signal from a lock sensor or a rotation sensor are connected to the motor.
Those wires are axially pulled out along a side surface of the housing so as not to protrude from an outer shape of flanges provided at axial ends of the housing, and are then pulled out via a wire-outlet port formed in one of the flanges. This configuration prevents the wires from being caught by or brought into contact with something in the electronic device, and damages of the wires are therefore prevented.
In general axial fan units, many wires are pulled out from respective axial fans. Thus, the air-outlet port via which the wires are pulled out to the outside of the axial fan unit has to be sufficiently large. In order to achieve this, there are two approaches. The first approach is to increase the size of the flange and housing. The second approach is to reduce a diameter of a path for an air flow, which is formed on a center-axis side of the wire-outlet port, i.e., an inner diameter of the housing, without changing the size of the flange. The reduction in the inner diameter of the housing makes it difficult to provide both a required air flow rate and a required static pressure. Moreover, considering recent increase in power consumption of the motor of the axial fan, another approach, i.e., to reduce a diameter of each wire in order to prevent the size increase of the wire-outlet port is impractical.
Growing diversity of axial fan unit design has raised the possibility that the position at which the wires are pulled out from the axial fan unit is varied depending on a wiring technique employed in a product incorporating the axial fan unit therein. However, conventional axial fans are designed such that the wires are pulled out from the axial fan unit at an unchanged position. Thus, it is difficult to change the position at which the wires are pulled but from the axial fan unit.